The present invention relates generally to devices for aligning the steering structure of a wheeled vehicle. In particular, it relates to tools used to define the rotational position of a bushing in aligning the steering structure of a wheeled vehicle.
It is necessary to maintain proper wheel alignment in many vehicles, particularly automobiles. Many methods of adjusting wheel alignment in vehicles are known in the art. Typically, camber and caster must be periodically adjusted.
Camber is defined as the angle between a line extending through the centerline of a typical steering knuckle and the centerline of the tire, as viewed from the rear of the vehicle. A vehicle has a slight positive camber when the top of the tire is tipped outwardly away from the side of the vehicle. It is known in the art that a slight positive camber, which is measured in degrees, prevents premature tire wear by compensating for deflections in the steering axle and by compensating for road bed crowns.
Caster is a measure of the angle between the centerline of typical steering knuckle and the vertical, as viewed from the side of the vehicle. A wheel having a slight positive caster has a steering knuckle axis that is tipped slightly toward the rear of the vehicle from the vertical. A slight positive caster causes the vehicle to track more easily, and improves steering stability.
Caster and camber settings are typically specified in the design of an automobile, and preset in the manufacturing facility. Poor road conditions, vehicle accidents, and normal wear cause steering assemblies to fall out of adjustment. Many devices have been invented for the purpose of adjusting camber and caster in vehicles. The type of device needed for a particular vehicle may depend upon the configuration of the steering structure.
For example, Dickerson et al. U.S. Pat. No. 4,232,880 discloses an adjusting sleeve for adjusting the camber of a wheel assembly. Drotar et al. U.S. Pat. No. 4,509,772 discloses a similar adjusting sleeve for simultaneously adjusting camber and caster in a wheel assembly. In order for the sleeve to function properly, the sleeve cannot rotate. Ingalls U.S. Pat. No. 4,400,007 discloses an adjusting sleeve with a locking mechanism for preventing rotation of the sleeve after installation.
The Drotar et al. U.S. Pat. No. 4,509,772 is a typical example of an invention which simultaneously adjusts both camber and caster. Because camber and caster usually cannot be independently adjusted, the task of achieving acceptable readings for both is often difficult. This dependence often makes the task of alignment more of an art than a science.
The prior art has attempted to address the problem of simultaneous camber and caster adjustment by providing alignment devices having indicators which allow the repairman to make steering assembly adjustments without having to perform unnecessary remeasuring and reassembling steps.
Koch et al. U.S. Pat. No. 3,342,507 discloses a mechanism for adjusting camber in heavy axled vehicle having kingpin construction. The Koch et al. Patent describes the use of a position indicator on the kingpin to determine a desired rotational position of a bushing surrounding the kingpin. Adjustments in camber require shimming between the spring pad and the spring to restore caster.
Specktor et al. U.S. Pat. No. 4,684,150, assigned to the same assignee as the present application, discloses a camber and toe adjustment mechanism consisting of a tapered shim having indicia on the shim surface. The shim is placed between the wheel mount and the end plate of a wheel axle.
Although camber and camber adjustment with the use of position indicators are known in the art, few inventions disclose the use of special tools to adjust alignment. Kost et al. U.S. Pat. No. 2,923,555 discloses a camber, toe and caster adjustment mechanism for truck wheel mounting. The Kost et al. U.S. Pat. No. 2,923,555 includes a removable scale for adjusting the position of a bearing supporting a steering joint. The scale extends roughly one third the way around the adjustment nut, and is removably attached to the front axle.
Specktor et al. U.S. Pat. No. 4,641,853, assigned to the same assignee as the present application, discloses an adjustment bushing and a removable scale for adjusting camber and caster. The bushing has an outer cylindrical surface. The removable scale is positioned on the outer cylindrical surface, and must be removed before the bushing is installed. The mechanic cannot check to make sure the bushing is properly positioned once the bushing has been installed.